Means for silencing receivers during operation of transmitters



March 31, 1942. E TOT 2,277,731

v MEANS FOR SILENCING- A RECEIVER DURING OPERATION OF A TRANSMITTER Filed Jan. 22, 1941 7 (51 0 Pate/722a!) INVENTOR fmericlr 7'0;

A TT'ORNE Y Patented Mar. 31, 1942 MEANS FOR ING OPERATION 4 Claims.

This invention relates to a means to silence a radio receiver which is being used in conjunction with a transmitter keyed by removing a negative blocking bias from its master oscillator grid or an amplifier grid. It is an object of this invention to provide such a means which will allow any degree of receiver silencing which is found desirable. The single figure of the drawing is a diagrammatic view of the circuit used in carrying out the invention.

In the drawing D1 and D2 indicate two diodes which may be separate or may be in the form of a duplex diode. They are so connected that when unblocked or operative they together will pass a complete alternating current wave as impressed on the secondary of transformer T1 upon which is normally impressed the R. F. or I. F. signal received by the receiver. The output of these diodes is taken ofi by means of line L1 to the A. F. channel, the line L1 connecting through coupling condenser C2 to a point in the plate-cathode circuit of diode D2 located between filter resistor R2 and load resistor R3. An R. F. filter condenser C3 is shunted around resistances R2 and B3. A bypass condenser C1 is located between the plate of D1 and the cathode of D2. The diode D2 in conjunction with its associated circuit components C2, C3, R2, and R3 operates normally as a detector of the R. F. and I. F. si nal impressed upon transformer T1. The key K1 serves to ground the grid of the oscillator or of some amplifier stage in the transmitter, thereby removing the blocking [negative] bias impressed upon the aforesaid grid by voltage E1 through resistors R1 and R5. Resistor R5 protects .the voltage source E1 from direct short circuit to ground and R4 serves to filter the transmitter grid circuit. The plate of diode D1 is connected to the key through resistor R1 which may be variable.

The diode D1 in conjunction with components C1 and R1 operates as a silencing device in the following manner: The plate of D1 is normally biased negative by bias voltage E1 acting through resistors R1 and R5. When key K1 is closed, the bias voltage acting on the plate of D1 is reduced to zero and the diode D1 becomes conductive on alternate half cycles of the R. F. or I. F. signal voltage. If the resistance of R1 is zero this efiectively prevents rectification by D2 by providing conductance in the opposite direction. Since each of the diodes pass on alternate half cycle of the signal wave form, there will be no response in the A. F. channel. However, by varying the value of R1, the effectiveness of diode SILENCING RECEIVERS DUR- OF TRANSMITTERS Emerick Toth, Cheverly, Md. Application January 22, 1941, Serial No. 375,419

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3'70 0. G. 757) D1 can be varied from the completely efi'ective condition just described to one which allows any desired response up to complete rectification by diode D2. As the value of this resistor is increased above zero a D. C. bias is built up at the plate of D1. This in conjunction with condenser C1 serves to limit the effectiveness of D1 in opposition to D2. By properly selecting the values of R1 and C1 it is possible as stated above to adjust the degree of silencing attained between wide limits. Typical circuit values could be as follows: D1, Dz=fiH6 diode; C1=0.l mf.; 02:.005 mi.; C3=Z50 mmi; R1=0 to 1 megohm; R2=50,000 ohm; R3=250,000 ohm; R4=l000 ohm; R5=l0,000 ohm; E1=50 volts D. C.

While the disclosure has been restricted to What is now considered the preferred form of the invention, it is to be understood that the invention is to be limited only by the scope and limits of the appended claims.

The invention described herein may be manuiactured and/or used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. Means adapted to silence a receiver during the operation of a transmitter having a key, comprising a pair of half wave rectifiers each so connected as to pass, when conducting, an alternate half cycle of the R. F. signal wave received by said receiver, means normally blocking one or said rectifiers and means operated by the key or said transmitter to unblock said normally blocked rectifier.

2. Means adapted to silence a receiver during the operation or a transmitter having a key, comprising a pair or half wave rectifiers each so connected as to pass, when conducting, an alternate half cycle of the R. F. signal wave received by said receiver, means normally blocking one or said rectifiers, means operated by the key of said transmitter to unblock said normally blocked rectifier, and means to vary the degree of the unblocking action of said unblocking means.

3. Means adapted to silence a receiver during the operation of a transmitter, comprising a pair of diodes, each so connected as to pass, when conducting, an alternate half cycle of the R. F. signal wave received by said receiver, a 7

source of voltage, means normally app yin said voltage to said transmitter and to one of said diodes in a manner to block the operation of said diode and said transmitter, and means for simultaneously removing said blocking voltage from said diode and said transmitter.

4. Means adapted to silence a receiver during the operation of a transmitter, comprising a detector circuit having two branches, a pair of diodes connected across said branches in such a manner that each, when unblocked, will be conducting in the opposite direction to the other, means leading the output of said diodes to the A. F. channel of said receiver, a source of voltage, means applying said voltage to the plate of one of said diodes and to said transmitter in a manner to block said diode and said transmitter, means to regulate the value of said voltage as applied to said plate and means to simultaneously remove said blocking voltage from said plate and said transmitter.

EMERICK TOTH. 

